It's important to avoid the exchange since the pair of bishops is precisely one of the reasons for White's advantage.
12... d5f6 A rare move. The players with Black usually accept the pawn sacrifice. 13. f1d3  13... b7b6 This move has never been played before, according to my database. Black wants to continue the thematic development of the bishop on a6. 14. e3e4  14... c8a6 